JP3909663B2 - Piezoelectric parts - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric component used as, for example, a resonator or an oscillator. This type of piezoelectric component can be used for a clock of a microcontroller of a mobile phone, a CD-ROM drive, or an in-vehicle electronic device.
[0002]
[Prior art]
Various types of piezoelectric parts of this type have been proposed and put to practical use. For example, Japanese Patent Laid-Open No. 2001-53573 discloses a piezoelectric component having a vibration space that is less likely to fail and has a high degree of airtightness.
[0003]
In this type of piezoelectric component, the basic natural resonance frequency is inversely proportional to the thickness of the piezoelectric ceramic substrate. Therefore, when the resonance frequency is increased, the thickness of the piezoelectric ceramic substrate must be reduced correspondingly.
[0004]
As means for avoiding this problem, a piezoelectric component using a high-order harmonic, typically a third-order harmonic vibration mode, is known instead of the fundamental vibration mode. In this type of piezoelectric component, the thickness of the piezoelectric ceramic substrate can be increased as compared with the case where the fundamental wave is used, reliability can be ensured, and mass production can be easily performed.
[0005]
However, in recent years, the demand for miniaturization of electronic parts has increased, and piezoelectric parts cannot be an exception. When the size of the piezoelectric component is reduced and the oscillation frequency is increased, the problem is how to suppress the influence of the fundamental wave on the thickness longitudinal third harmonic vibration mode.
[0006]
[Problems to be solved by the invention]
The subject of this invention is providing the piezoelectric component which can suppress the influence of the fundamental wave vibration mode with respect to the thickness longitudinal third harmonic vibration mode which it is going to utilize as much as possible.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, a piezoelectric component according to the present invention includes a piezoelectric element, a first cavity layer, a first sealing layer, a second cavity layer, and a second sealing layer. In addition, the vibration mode of the thickness third harmonic is used.
[0008]
The piezoelectric element has front and back electrodes opposed to each other on the front and back surfaces in the thickness direction of the piezoelectric ceramic substrate.
[0009]
One surface of the first cavity layer is adjacent to the surface of the piezoelectric ceramic substrate, and a first cavity is formed around the vibrating portion including the surface electrode.
[0010]
One surface of the first sealing layer is adjacent to the other surface of the first cavity layer and seals the first cavity.
[0011]
One surface of the second cavity layer is adjacent to the back surface of the piezoelectric ceramic substrate, and a second cavity is formed around the vibrating portion including the back electrode.
[0012]
One surface of the second sealing layer is adjacent to the other surface of the second cavity layer, and seals the second cavity.
[0013]
The thickness t (μm) of the first and second cavity layers is the absolute value of the reactance component X of the piezoelectric element between the resonance frequency and the anti-resonance frequency viewed from the frequency resonance characteristics of the piezoelectric element. When the maximum value of the electrical characteristic Q obtained by dividing by the resistance component R is Qmax, the maximum value Qmax (3rd) for the third harmonic is higher than the maximum value Qmax (1st) for the fundamental wave. Has been selected.
[0014]
As described above, in the piezoelectric component according to the present invention, the piezoelectric element has the front electrode and the back electrode facing each other on the surface and the back surface in the thickness direction of the piezoelectric ceramic substrate. Vibration characteristics can be obtained.
[0015]
The first cavity layer forms a first cavity around the vibration part including the surface electrode. The first sealing layer is provided on the first cavity layer and seals the first cavity. The second cavity layer forms a second cavity around the vibration part including the back electrode. The second sealing layer is provided on the second cavity layer and seals the second cavity. Accordingly, the piezoelectric element is substantially determined by the thickness t of the first and second cavity layers, and the first cavity and the second cavity sealed by the first sealing layer and the second sealing layer. Piezoelectric vibration is performed in the inside.
[0016]
Furthermore, in the piezoelectric component according to the present invention, the maximum value Qmax (3rd) for the third harmonic is selected to be higher than the maximum value Qmax (1st) for the fundamental wave. Therefore, the third harmonic vibration mode is superior to the fundamental wave vibration mode, and a piezoelectric component using the third harmonic vibration mode, specifically, the third harmonic vibration mode can be realized.
[0017]
In the present invention, the superiority of the third harmonic vibration mode over the fundamental vibration mode is obtained by selecting the thickness t (μm) of the first and second cavity layers. That is, the fundamental wave vibration mode is suppressed by selecting the thickness t (μm) of the first and second cavity layers. As described above, in the present invention, the fundamental wave vibration mode is suppressed by a relatively simple means of selecting the thickness t (μm) of the first and second cavity layers, so that industrial mass production is easy.
[0018]
According to the experiments by the inventors, when the wavelength of the third harmonic is λ (μm) in the range of thickness t (μm), the fundamental vibration mode is suppressed by satisfying t> 0.1λ, It has been found that Qmax (3rd)> Qmax (1st) can be satisfied.
[0019]
From the viewpoint of suppressing the fundamental wave vibration mode, the thickness t may be large, but in this case, the thickness of the entire piezoelectric component increases, which is against the demand for downsizing. In order to meet such a practical requirement, it is preferable to satisfy t ≦ 60 μm.
[0020]
The present invention can be applied to, for example, a filter in addition to a resonator or an oscillator. Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The accompanying drawings are merely examples.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
1 is an exploded perspective view of a piezoelectric component according to the present invention, FIG. 2 is a perspective view showing an assembled state of the piezoelectric component shown in FIG. 1, and FIG. 3 is an enlarged cross-sectional view taken along line 3-3 in FIG. . The illustrated embodiment shows an example of an energy confinement type that is suitable for use as a resonator or an oscillator, and that operates in a thickness longitudinal vibration mode. The illustrated piezoelectric component includes a piezoelectric element 1, a first cavity layer 21, a first sealing layer 22, a second cavity layer 31, and a second sealing layer 32.
[0022]
The piezoelectric element 1 includes a piezoelectric ceramic substrate 11, a front electrode 12, and a back electrode 13. The piezoelectric ceramic substrate 11 is polarized in the thickness direction. The front electrode 12 has a front lead electrode 14 and is provided on the surface of the piezoelectric ceramic substrate 11. The front lead electrode 14 is electrically connected to the front electrode 12, and the end portion is led out to the side edge of the piezoelectric ceramic substrate 11. The back electrode 13 is provided on the back surface of the piezoelectric ceramic substrate 11 and faces the front electrode 12. The front electrode 12 and the back electrode 13 constitute a vibration part.
[0023]
The back lead electrode 15 is electrically connected to the back electrode 13, and an end portion thereof is led out to a side edge of the piezoelectric ceramic substrate 11. As the constituent material of the piezoelectric ceramic substrate 11, conventionally known materials can be used. The front electrode 12, the back electrode 13, the front lead electrode 14, and the back lead electrode 15 can be formed by application of thin film technology or thick film technology such as sputtering or vapor deposition.
[0024]
The first cavity layer 21 is attached to the surface of the piezoelectric ceramic substrate 11 and forms the first cavity 6 around the surface electrode 12. The first cavity layer 21 has a first hole in the center, and the first hole constitutes the first cavity 6. As the first hollow layer 21, a thermosetting resin, specifically, an epoxy resin can be used.
[0025]
The first sealing layer 22 is a thermosetting resin, and is attached on one surface of the first cavity layer 21 to seal the first cavity 6. The layer thickness of the first sealing layer 22 is set in a range of 3 μm to 50 μm, for example. Furthermore, a resin sheet can be used for the first sealing layer 22.
[0026]
The second cavity layer 31 is attached to the back surface of the piezoelectric ceramic substrate 11 and forms the second cavity 7 around the back electrode 13. The second cavity layer 31 has a second hole in the center, and this second hole constitutes the second cavity 7. As the second hollow layer 31, a thermosetting resin, specifically, an epoxy resin can be used.
[0027]
The second sealing layer 32 is provided on the second cavity layer 31 and seals the second cavity 7. The layer thickness of the second sealing layer 32 is set in a range of 3 μm to 50 μm, for example. The second sealing layer 32 can also use a thermosetting resin. Specifically, it is an epoxy resin.
[0028]
The first cavity layer 21, the first sealing layer 22, the second cavity layer 31, and the second sealing layer 32 can be formed, for example, by applying a thermosetting resin by screen printing.
[0029]
The thickness t of the first cavity layer 21 and the second cavity layer 31 is an absolute value of the reactance component X of the piezoelectric element between the resonance frequency fr and the antiresonance frequency fa as seen from the frequency resonance characteristic of the piezoelectric element 1. Electrical characteristics Q obtained by dividing the value by the resistance R,
Q = | X | / R
Is selected such that the maximum value Qmax (3rd) for the third-order harmonic used is higher than the maximum value Qmax (1st) for the fundamental wave. The thickness t of the first cavity layer 21 and the thickness t of the second cavity layer 31 may be the same as or different from each other.
[0030]
As described above, the thickness t of the first cavity layer 21 and the second cavity layer 31 is set so that the maximum value Qmax (3rd) for the third harmonic is higher than the maximum value Qmax (1st) for the fundamental wave. Therefore, the third harmonic vibration mode is superior to the fundamental wave vibration mode.
[0031]
The superiority of the third harmonic vibration mode with respect to the fundamental vibration mode is obtained by selecting the thickness t (μm) of the first and second cavity layers 21 and 31. That is, the fundamental wave vibration mode is suppressed by selecting the thickness t (μm) of the first and second cavity layers 21 and 31. As described above, in the present invention, the fundamental wave vibration mode is suppressed by a relatively simple means of selecting the thickness t (μm) of the first and second cavity layers 21 and 31, so that industrial mass production can be easily performed. It is.
[0032]
FIG. 4 is data showing the relationship between the thickness t (μm) of the first and second hollow layers 21 and 31 and the maximum value Qmax of the electrical characteristic Q for the piezoelectric component according to the present invention. This data is obtained when the frequency of the third harmonic is 33.86 MHz in the piezoelectric component having the structure shown in FIGS. In FIG. 4, the horizontal axis represents thickness t (μm), and the vertical axis represents Qmax. The scale on the horizontal axis is shown using the wavelength λ of the third harmonic. Characteristic CH1 indicates the characteristic of the fundamental wave vibration mode, and characteristic CH3 indicates the characteristic of the third harmonic vibration mode.
[0033]
As shown in FIG. 4, in the range where the thickness t (μm) is larger than 0.1λ , the maximum value Qmax (3rd) for the third harmonic F3 is larger than the maximum value Qmax (1st) for the fundamental wave. Yes. This is presumably because the suppression action of the fundamental wave vibration mode by the first and second cavity layers 21 and 31 works effectively in the region where the thickness t is larger than 0.1λ . A particularly preferable range of the thickness t is a region of 0.21λ or more. According to the data of FIG. 4, in this region, Qmax ≧ 3 that must be satisfied with this type of piezoelectric component is cleared.
[0034]
From the standpoint of suppressing the fundamental wave vibration mode, the thickness t may be larger, but this increases the thickness of the entire piezoelectric component, which is against the demand for miniaturization. In order to meet such a practical requirement, it is preferable to satisfy t ≦ 60 μm.
[0035]
Further, in the embodiment of FIGS. 1 to 3, the front electrode 12 is provided on the front surface of the piezoelectric ceramic substrate 11, and the back electrode 13 is provided on the back surface of the piezoelectric ceramic substrate 11 and faces the front electrode 12. The front electrode 12 and the back electrode 13 constitute a vibration part. Therefore, the piezoelectric vibration characteristic by the front electrode 12 and the back electrode 13 is obtained.
[0036]
The first cavity layer 21 forms the first cavity 6 around the vibration part including the surface electrode 12. The first sealing layer 22 is provided on the first cavity layer 21 and seals the first cavity 6. The second cavity layer 31 forms the second cavity 7 around the vibration part including the back electrode 13. The second sealing layer 32 is provided on the second cavity layer 31 and seals the second cavity 7. Accordingly, the piezoelectric element 1 is determined by the thickness t of the first and second cavity layers, and the first cavity 6 and the second cavity sealed by the first sealing layer 12 and the second sealing layer 22 are used. Piezoelectric vibration is performed inside the two cavities 7.
[0037]
The first cavity layer 21 has a first hole penetrating with the same width in the layer thickness direction, and forms the first cavity 6 by the first hole around the surface electrode 12. Since the first hole constituting the first cavity 6 penetrates with the same width in the layer thickness direction of the first cavity layer 21, the resist resin normally used for forming the first cavity 6 is completely removed. Can be removed. For this reason, the characteristic defect by the residue of resist resin can be avoided.
[0038]
In the embodiment, the first sealing layer 22 is a thermosetting resin and is formed on one surface of the first cavity layer 21 to seal the first cavity 6. Such a first sealing layer 22 may be formed on one surface of the first cavity layer 21, so that the first sealing layer 22 need not be aligned with the first cavity layer 21. . For this reason, the failure of the airtightness due to the displacement does not occur.
[0039]
In addition, since the first sealing layer 22 may be formed planarly with respect to one surface of the first cavity layer 21, a vibration space having a high degree of airtightness can be formed. Further, by forming the first sealing layer 22 in a plane with respect to the first cavity layer 21, a sufficient formation area is ensured, so that a vibration space in which the hermeticity is not easily broken is obtained.
[0040]
The 1st sealing layer 22 can also adhere sheet-like resin. Also in this case, the first sealing layer 22 only needs to be attached to the one surface of the first cavity layer 21 in a planar manner, so that the first sealing layer for the first cavity layer 21 that has been conventionally required is sealed. Positioning of the stop layer 22 becomes unnecessary. For this reason, the failure of the airtightness due to the displacement does not occur.
[0041]
Furthermore, the internal volume of the first cavity 6 is set to a certain spatial volume determined by the plane area of the first hole provided in the first cavity layer 21 and the layer thickness of the first cavity layer 21. The For this reason, certain characteristics can be ensured.
[0042]
In the embodiment, a top plate 23 and a base substrate 4 are further included. The top plate 23 is bonded onto the first sealing layer 22 by thermocompression bonding. The top plate 23 can be composed of a ceramic sheet or an aramid sheet.
[0043]
The base substrate 4 includes a base body 40, a first terminal electrode 41, and a second terminal electrode 42. In the embodiment, the third terminal electrode 43 is also illustrated. The base substrate 4 supports the piezoelectric element 1, the first cavity layer 21, the first sealing layer 22, the second cavity layer 31, and the second sealing layer 32 on one surface side of the base body 40. To do. Thereby, the reinforcement effect | action by the base substrate 4 is obtained, and a piezoelectric component with high mechanical strength is obtained.
[0044]
The first terminal electrode 41 is formed on the side end surface from which the front lead electrode 14 is led out, and the second terminal electrode 42 is formed on the side end surface from which the back lead electrode 15 is led out. The base 40 constituting the base substrate 4 can be made of ceramic.
[0045]
In the embodiment, the first terminal electrode 41 to the third terminal electrode 43 are formed in a band shape around the assembly at a distance from each other, and the band electrode on the top plate side is separated at the center portion. May be. In the first terminal electrode 41 to the third terminal electrode 43, the lowermost layer and the uppermost layer in contact with the base body 40 are silver layers formed by baking, and these silver layers are electrically connected by a thin film. In addition, a nickel plating layer is provided on the silver layer to prevent solder erosion, and a tin plating layer or solder plating layer is provided on the nickel layer to improve the solderability. can do.
[0046]
5 to 17 show the manufacturing process of the piezoelectric component shown in FIGS. 1 to 3 and having a piezoelectric component of 33.86 MHz. First, as shown in FIGS. 5 and 6, a large number of front electrodes 12 and back electrodes 13 are formed in a predetermined pattern on the front and back surfaces of a large wafer-like piezoelectric ceramic substrate 11. The front electrode 12 and the back electrode 13 form a pattern by masking using a thin film method. Alternatively, it can be formed by a high-precision pattern forming technique using photolithography, or can be formed by screen printing or the like. The front electrode 12 and the back electrode 13 are formed as a pattern having the front lead electrode 14 and the back lead electrode 15.
[0047]
The piezoelectric ceramic substrate 11 is previously polarized in the thickness direction according to a known technique, and the front electrode 12 and the back electrode 13 are formed on the polarized region. In forming the front lead electrode 14 and the back lead electrode 15, the front electrode 12 and the back electrode 13 are formed by, for example, sputtering or vapor-depositing a 10 nm Cr film and a 1.2 μm Ag film thereon as a base film. . The front electrode 12 and the back electrode 13 have a short shape of 0.5 × 0.4 mm, for example. However, the shape may be a circle, an ellipse, or a short shape with R.
[0048]
In the polarization treatment prior to electrode formation, the piezoelectric ceramic substrate 11 was subjected to primary polishing so as to have a thickness of 0.35 mm, and then a 1 μm Cu polarized electrode film was deposited on both sides of the piezoelectric substrate 11. Thereafter, the piezoelectric ceramic substrate 11 was put in silicon oil, a polarization voltage of 9 kV / mm was applied to the Cu polarization electrode film, and a polarization treatment was performed for 1000 seconds under a temperature condition of 150 ° C.
[0049]
Next, as shown in FIGS. 7 and 8, resist resins 60 and 70 covering the front electrode 12 and the back electrode 13 in a range larger than the outer diameter thereof were applied and dried. As the resist resins 60 and 70, those which can be easily dissolved and removed with water, alkali or organic solvent are used.
[0050]
Next, as shown in FIGS. 9 and 10, resins 21 and 31 are applied to the front and back surfaces of the wafer-like piezoelectric ceramic substrate 11 so as to fill the regions without the resist resins 60 and 70, dried, and fixed. I let you.
[0051]
The resins 21 and 31 constitute the first and second hollow layers 21 and 31 (see FIGS. 1 to 3). Resins 21 and 31, in accordance with the teachings of the data shown in FIG. 4, as the thickness t after drying is greater than 0.1 [lambda], more preferably formed to have a higher 0.21Ramuda. However, it is formed to be 60 μm or less in order to meet the demand for thinning. As the first and second hollow layers 21 and 32, a thermosetting resin, specifically, for example, an epoxy resin that is permanently cured at 150 ° C. for about 30 minutes can be used.
[0052]
Next, as shown in FIGS. 11 and 12, the resist resins 60 and 70 are removed. As described above, the resist resins 60 and 70 can be easily dissolved and removed with water, an alkali, or an organic solvent. After the resist resins 60 and 70 are removed, spaces 6 and 7 that become the first cavity and the second cavity are generated. The first hole constituting the first cavity 6 and the second hole constituting the second cavity 7 have the same width in the layer thickness direction of the first cavity layer 21 and the second cavity layer 31. Since it penetrates, the resist resins 60 and 70 can be discharged in the plane direction of the first cavity layer 21 and the second cavity layer 31 and completely removed. For this reason, the characteristic defect by the residue of the resist resins 60 and 70 can be avoided.
[0053]
Next, as shown in FIGS. 13 and 14, the first sealing layer 22 and the second sealing layer 32 are stacked. As the laminating means, means such as screen printing or sheet pasting can be used. Thus, an assembly including the wafer-like piezoelectric ceramic substrate 11, the first sealing layer 22, and the second sealing layer 32 is obtained. The first and second sealing layers 22 and 32 can be made of a thermosetting resin. Specifically, for example, it is an epoxy resin that is fully cured at 80 ° C. for about 60 minutes.
[0054]
In this case, the first and second sealing layers 22 and 32 may be formed in a plane with respect to one surface of the first and second cavity layers 21 and 31, so that the first and second cavities are formed. The alignment of the first and second sealing layers 22 and 32 with respect to the layers 21 and 31 is not necessary. For this reason, the failure of the airtightness due to the displacement does not occur.
[0055]
In addition, the first and second sealing layers 22 and 32 may be formed in a plane with respect to one surface of the first and second cavity layers 21 and 31, so that the vibration space has a high degree of airtightness. Can be formed. Further, the planar stacking of the first and second sealing layers 22 and 32 with respect to the first and second cavity layers 21 and 31 ensures a sufficient stacking area, and therefore vibrations that are less likely to cause an airtight breakdown. Space is obtained.
[0056]
Further, the internal volumes of the first and second cavities 6 and 7 are determined by the plane areas of the first and second holes provided in the first and second cavity layers 21 and 31 and the first and second cavities. It is set to a certain spatial volume determined by the layer thickness of the hollow layers 21 and 31. For this reason, certain characteristics can be ensured.
[0057]
Next, as illustrated in FIGS. 15 and 16, the base substrate 4 is bonded to the second sealing layer 32, and the top plate 23 is bonded to the first sealing layer 22. In bonding the base substrate 4 and the top plate 23, the adhesive force of the second sealing layer 32 and the first sealing layer 22 is used, or the second sealing layer 32 and the first sealing layer are used. The adhesive force of the adhesive layer applied to the surface of the layer 22 can be utilized.
[0058]
The base substrate 4 is manufactured in a separate process from the process of manufacturing the assembly including the piezoelectric element 1, the first sealing structure 2, and the second sealing structure 3. The base substrate 4 preferably has a first terminal electrode 41, a second terminal electrode 42, and a third terminal electrode 43 formed in a band shape on the bottom surface thereof. Between the adjacent piezoelectric elements, the first terminal electrode 41 and the second terminal electrode 42 are integrally formed.
[0059]
Next, as shown in FIG. 17, the base substrate 4, the wafer-like piezoelectric ceramic substrate 11, the first cavity layer 21, the first sealing layer 22, the second cavity layer 31, and the second sealing layer 32. And the assembly including the top plate 23 are cut along the X1-X1 line, the X2-X2 line, and the (Y1-Y1 line) to (Y3-Y3 line). As the cutting means, a dicing saw can be used. Through this cutting step, a single piezoelectric component can be obtained.
[0060]
Then, the 1st terminal electrode 41, the 2nd terminal electrode 42, and the 3rd terminal electrode 43 are formed in the side surface of an assembly (refer FIGS. 1-3). As a result, the end of the first terminal electrode 41 is conducted to the end of the front lead electrode 14, and the end of the second terminal electrode 42 is conducted to the end of the back lead electrode 15 (FIGS. 1 to 3). reference). The first terminal electrode 41 to the third terminal electrode 43 can be formed by forming a thin film by thin film forming means such as vapor deposition or sputtering and then plating.
[0061]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a piezoelectric component that can suppress the influence of the fundamental wave vibration mode to the third harmonic vibration mode to be used as much as possible.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a piezoelectric component according to the present invention.
FIG. 2 is a perspective view of a piezoelectric component according to the present invention.
FIG. 3 is an enlarged cross-sectional view taken along line 3-3 in FIG.
FIG. 4 is data showing the relationship between the thickness t (μm) of the first and second cavity layers and the maximum value Qmax of the electrical characteristics Q for the piezoelectric component according to the present invention.
FIG. 5 is a perspective view showing a manufacturing process of a piezoelectric component according to the present invention.
6 is an enlarged cross-sectional view showing the step shown in FIG. 5;
7 is a perspective view showing a manufacturing step after the step shown in FIGS. 5 and 6. FIG.
8 is an enlarged sectional view showing the process shown in FIG. 7;
9 is a perspective view showing a manufacturing step after the step shown in FIGS. 7 and 8. FIG.
10 is an enlarged cross-sectional view showing the step shown in FIG. 9;
11 is a perspective view showing a manufacturing step after the step shown in FIGS. 9 and 10. FIG.
12 is an enlarged cross-sectional view showing the process shown in FIG. 11. FIG.
13 is a perspective view showing a manufacturing step after the step shown in FIGS. 11 and 12. FIG.
14 is an enlarged cross-sectional view showing the process shown in FIG. 13;
15 is a perspective view showing a manufacturing step after the step shown in FIGS. 13 and 14. FIG.
16 is an enlarged cross-sectional view showing the process shown in FIG. 15;
17 is a perspective view showing a manufacturing step after the step shown in FIGS. 15 and 16. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric element 11 Piezoelectric ceramic substrate 21 1st cavity layer 22 1st sealing layer 31 2nd cavity layer 32 2nd sealing layer

Claims (4)

Piezoelectric component including a piezoelectric element, a first cavity layer, a first sealing layer, a second cavity layer, and a second sealing layer, and utilizing a vibration mode of a thickness third harmonic Because
The piezoelectric element has a front electrode and a back electrode facing each other on the front and back surfaces in the thickness direction of the piezoelectric ceramic substrate,
One surface of the first cavity layer is adjacent to the surface of the piezoelectric ceramic substrate and forms a first cavity around the vibrating portion including the surface electrode;
One surface of the first sealing layer is adjacent to the other surface of the first cavity layer and seals the first cavity.
The second cavity layer is adjacent to the back surface of the piezoelectric ceramic substrate and forms a second cavity around the vibrating portion including the back electrode,
The second sealing layer has one surface adjacent to the other surface of the second cavity layer and sealing the second cavity,
The thickness t (μm) of the first and second cavity layers is the absolute value of the reactance component X of the piezoelectric element between the resonance frequency and the anti-resonance frequency seen from the frequency resonance characteristic of the piezoelectric element. When the maximum value of the electrical characteristic Q obtained by dividing by the resistance component R is Qmax, the maximum value Qmax (3rd) for the third harmonic is higher than the maximum value Qmax (1st) for the fundamental wave. Has been selected
The wavelength of the third harmonic is λ (μm), and t> 0.1λ is satisfied.
Piezoelectric parts.   2. The piezoelectric component according to claim 1, wherein the wavelength of the third harmonic is λ (μm) and satisfies t ≧ 0.21λ.   The piezoelectric component according to claim 1, wherein the piezoelectric component satisfies t ≦ 60 μm.   4. The piezoelectric component according to claim 1, wherein the piezoelectric component uses a third harmonic vibration mode.

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